For the logo you should just be able to use the "W" from the blueprint. But whenever you need to type the Wikipedia "W" you will need to insert it as a special character.
You can insert it by typing its Unicode: U+e02f , or see the image to the right.

Illustrator

Illustrator supports a very convenient method to insert special characters: The Glyphs.
You can find Glyphs at the "Top Navigation": "Type": "Glyphs.

Inkscape

Depending on your platform, you should be able to insert a character from your system's "Character Map" software. Use the Linux Libertine O font and character U+E02F from the private use area. Alternatively, you can highlight and copy this character: .